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What is the principle of writeConcern in MongoDB? I believe many inexperienced people don't know what to do about it. Therefore, this paper summarizes the causes and solutions of the problem. Through this article, I hope you can solve this problem.

Analysis of the principle of MongoDB writeConcern

MongoDB allows the client to flexibly configure the write policy (writeConcern) to meet the needs of different scenarios.

Db.collection.insert ({x: 1}, {writeConcern: {w: 1}})

WriteConcern option

The following WriteConncern options are supported by MongoDB

W: the data is written to the number nodes before it is confirmed to the client.

{w: 0} the write to the client does not need to send any acknowledgement, so it is suitable for scenarios with high performance requirements but no attention to correctness.

{w: 1} default writeConcern. When data is written to Primary, an acknowledgement is sent to the client.

{w: "majority"} data is written to most members of the replica set and an acknowledgment is sent to the client, which is suitable for scenarios that require high data security. This option reduces write performance.

J: confirm to the client after the journal of the write operation is persisted

The default is "{j: false}. If you require Primary writes to be persistent before confirming to the client, specify this option as true."

Wtimeout: write timeout, valid only if the value of w is greater than 1.

When {w:

}, the data needs to be successfully written to number nodes to be considered successful. If there is a node failure during the writing process, this condition may not be met and the confirmation result cannot be sent to the client. In this case, the client can set the wtimeout option to specify the timeout period. If the writing process continues beyond this time and does not finish, the write fails.

After reading the above, have you mastered the principle of writeConcern in MongoDB? If you want to learn more skills or want to know more about it, you are welcome to follow the industry information channel, thank you for reading!

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